Electrical systems, which can also be referred to as electrical apparatuses, often include both a silicon ground and a remote ground. The silicon ground (which can also be referred to as a local ground, an analog ground, or Agnd) is the ground associated with a die or chip. The remote ground (which can also be referred to as Rgnd, a return ground, or Rrtn) is the ground associated with a printed circuit board (PCB) to which the die or chip is attached.
To improve the accuracy of such systems, remote differential voltage sensing circuits (sometimes alternatively referred to as differential remote voltage sensing circuits) are often used. FIG. 1 illustrates a convention remote differential voltage sensing circuit 102 which includes two amplifiers, AMP1 and AMP2, and two resistor dividers to achieve remote sensing. One of the resistor dividers includes resistors R0 and R1, and the other one of the resistor dividers includes resistors R2 and R3. The two inputs to the remote differential voltage sensing circuit 102 in FIG. 1 are Vin and Rgnd, and the output of the remote differential voltage sensing circuit 102 is Vout, where Vout=Vin+Rgnd−Agnd. The conventional remote differential voltage sensing circuit 102 of FIG. 1 essentially functions as an analog calculation circuit.
Disadvantages associated with the conventional remote differential voltage sensing circuit 102 of FIG. 1 are that it takes up more silicon area than is desirable, it consumes more power than is desirable (because it includes two amplifiers), and it has a voltage offset (VOS) error that is greater than is desirable. More specifically, VOS=VOS1+2*VOS2, where VOS1 is the voltage offset error associated with the first amplifier (AMP1), VOS2 is the voltage offset error associated with the second amplifier (AMP2), and VOS is the total voltage offset error caused by the remote differential voltage sensing circuit 102 of FIG. 1.
To reduce power consumption, reduce silicon area, and reduce the voltage offset error, parallel transconductance (Gm) stages can be used to differentially sense a remote signal. An example of such a topology is illustrated in FIG. 2. More specifically, FIG. 2 illustrates a remote differential voltage sensing circuit 202 where the three inputs to the remote differential voltage sensing circuit 202 are Vin, Rgnd and Agrnd, and the output of the remote differential voltage sensing circuit 202 is Vout, where Vout=Vin+Rgnd−Agnd. Disadvantages associated with the remote differential voltage sensing circuit 202 of FIG. 2 are that it requires very good matching between the two input pairs, there is a common mode range limitation due to grounds as inputs, it still consumes more power than is desirable, and it still has a voltage offset (VOS) error that is greater than is desirable.